中的AsyncTask

Question

使用Looper.prepare我使用的AsyncTask了很多在我的項目，有時我收到此錯誤：

Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 

是受到關注的第一類是：

public class GetDetails extends 
     AsyncTask<String, String, JSONObject> { 

    public String URL = null; 
    public Activity context; 
    private boolean success = false; 
    private String id; 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     linlaHeaderProgress.setVisibility(View.VISIBLE); 

     // Get the application instance 
     AppsPlaceApplication.initInstance(); 
    } 

    @Override 
    protected JSONObject doInBackground(String... params) { 
//  Looper.prepare(); 

     HttpClient httpclient = new DefaultHttpClient(); 
     HttpPost httppost = null; 
     try { 
      httppost = new HttpPost(new URI(URL)); 
      List<BasicNameValuePair> nameValuePairs = new ArrayList<BasicNameValuePair>(); 
      nameValuePairs.add(new BasicNameValuePair("id", id)); 
      httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); 

      httppost.setHeader("Content-type", 
        "application/x-www-form-urlencoded"); 

      // Execute HTTP Post Request 
      HttpResponse response = httpclient.execute(httppost); 
      if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
       HttpEntity entity = response.getEntity(); 
       if (entity != null) { 
        InputStream in = entity.getContent(); 
        String result = HelperJsonStatic.convertStreamToString(in); 

       } 
      } else { 
       Toast.makeText(context, "", Toast.LENGTH_SHORT).show(); 
      } 
     } catch (URISyntaxException e1) { 
      e1.printStackTrace(); 
     } catch (ClientProtocolException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(JSONObject result) { 
     super.onPostExecute(result); 

    } 
} 

這是討厭，因爲我不明白爲什麼我應該使用looper。如果我使用Looper.prepare（）代碼行，經過一段時間後會崩潰，另一個錯誤告訴我每個線程只有一個Looper ... 有人可以解釋這件事，我做錯了什麼？這就像走在圈子裏。 謝謝。

Answer 1

問題是您從doInBackground()調用Toast.makeText().show()。你不能這樣做，因爲在後臺線程上調用了doInBackground()。您應該在onPostExecute()中顯示Toast。